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.Dd March 27, 2003
.Dt BUS_CHILD_PRESENT 9
.Os
.Sh NAME
.Nm bus_child_present
.Nd "ask the bus driver to see if this device is still really present"
.Sh SYNOPSIS
.In sys/param.h
.In sys/bus.h
.Pp
.In machine/bus.h
.In sys/rman.h
.In machine/resource.h
.Ft int
.Fn bus_child_present "device_t dev"
.Sh DESCRIPTION
The
.Fn bus_child_present
function requests that the parent device driver of
.Fa dev
check to see if the
hardware represented by
.Fa dev
is still physically accessible at this time.
While the notion of accessible varies from bus to bus, generally
hardware that is not accessible cannot be accessed via the
.Fn bus_space*
methods that would otherwise be used to access the device.
.Pp
This does not ask the question
.Dq does this device have children?
which can better be answered by
.Xr device_get_children 9 .
.Sh RETURN VALUES
A zero return value indicates that the device is not present in the
system.
A non-zero return value indicates that the device is present in the
system, or that the state of the device cannot be determined.
.Sh EXAMPLES
This is some example code.
It only calls stop when the
.Xr dc 4
device is actually present.
.Bd -literal -offset indent
device_t dev;
dc_softc *sc;

sc = device_get_softc(dev);
if (bus_child_present(dev))
	dc_stop(sc);
.Ed
.Sh SEE ALSO
.Xr device 9 ,
.Xr driver 9
.Sh AUTHORS
This manual page was written by
.An Warner Losh Aq Mt imp@FreeBSD.org .
